Synthesis of 9-aminoacridines by the [4 + 2] annulation of arynes and 2-aminobenzonitriles

Acridine derivatives, particularly 9-aminoacridines, are important nitrogen-containing heterocycles with broad pharmaceutical relevance. Herein, we report a metal-free and efficient strategy for the synthesis of 9-aminoacridines via a Kobayashi aryne-enabled annulation of 2-aminobenzonitriles. This transformation proceeds through a formal [4 + 2] annulation pathway, in which 2-aminobenzonitriles act as bifunctional synthons, enabling sequential nucleophilic addition and intramolecular cyclization. The reaction features readily accessible starting materials, operational simplicity, and broad substrate scope, affording a variety of substituted 9-aminoacridines in moderate to good yields. This method provides a straightforward and practical route to the biologically important 9-aminoacridine scaffold and further demonstrates the synthetic utility of aryne chemistry in nitrogen heterocycle construction.